Embodiments of the application described herein relate to a semiconductor memory device, and more particularly, relate to a nonvolatile memory device having a three-dimensional structure and a program method thereof.
Semiconductor memory devices are classified into volatile memory devices such as a DRAM, an SRAM, etc. and nonvolatile memory devices such as an EEPROM, a FRAM, a PRAM, an MRAM, a flash memory, etc. The volatile memory devices lose data stored therein at power-off, but the nonvolatile memory devices retain data stored therein even at power-off. In particular, the flash memory has merits such as fast program speed, low power consumption, storage of a large amount of data, etc. Thus, a flash memory system including the flash memory is widely used as a data storage medium.
The degree of integration of the flash memory is being increased to maintain excellent performance and a competitive price. However, a conventional two-dimensional flash memory has limits to increase the degree of integration due to a manufacturing process. A three-dimensional flash memory is being developed to overcome such limits.
The three-dimensional flash memory makes the degree of integration high, but its data reliability is decreased due to program disturbance or interference coupling between cells during a program operation. In particular, the data reliability may become more problematic when data of two or more bits is stored at a memory cell.